Gavin,

TP1 is your 60V rail
TP2 is your 42V rail
TP3 is ground for this part of the circuit.

If TP2 is reading 60V then the Zener CR6 is shot (1n4756a). Check R5 (10K). Until these are right - you will get no 42V and the Zener drops 18V.


At the junction "E5" - you should measure 5.6V. R12 (labelled as 0.33, 10% 5W) drops the 5.6V to 5V, at junction "E5". so check for the voltage drop across R12.

The 60V line measuring 75V could be Q1. Collector should measure 76V, Emitter 63.1V - Test Q1

If Q1 is playing up, then 76V -18 = 58V - which is close to the 60V you are seeing at TP2..

Sounds like Q1 Emitter / Collector short..

also check J1 Pins 7 and 8 for 60V AC.